Wilhelm schroder



UNITED STATES PATENT OFFICE.

WILHELM SCHRODER, OF 'WIEMELHAUSEN, GERMANY.

PROCESS OF MAKING YELLOW PRUSSIATE O'F POTASH.

SPECIFICATION forming part of Letters Patent No. 624,383, dated May 2, 1899.

Application filed October 21, 1898. Serial No. 694,175. (No specimens.)

To. all whom, it may concern:

Be it known that I, WILHELM ScHRonER, a

citizen of the Empire of Germany, residing at ing Yellow Prussiate of Potash in the Destructive Distillation of Goal, of which the following is a specification.

Analyses have shown that gaseous products of the distillation of coal after'having been relieved of ammonia contain per cubic meter of gas 0.7 grams of prussic acid, (GNH,) which quantity, in case it can be utilized for the manufacture of yellow prussiate, corresponds to 1.82 grams of crystallized prussiate of potash, (K,Fe(CN),,-3aq.) Consequently with a plant yielding one hundred thousand cubic meters of gas per day the production of ferrocyanide would amount to one hundred and eighty-two kilograms perday'or five thousand four hundred and sixty kilos per month, and the manufacture of prussiate of potash as a by-product of the destructive distillation of coal by means of an economical process is therefore a great desideratum. The following process has been found to answer this requirement:

To the water for the absorption of ammonia protochloride of iron (FeCl is added before the absorption takes place. When the water takes up ammonia, (NH the protochloride of iron (FeO1 contained in the water forms, with the ammonia, ferrous hydrate, (Fe(OH) 2,) besides salammoniac, (NH CL) With the sulphureted hydrogen contained in the gas it forms ferrous sulphide, (FeS,) which, together with the ferrous hydrate mentioned above, is held in suspension by the absorptionwater. Atthe same time the prussic acid combines with ammonia to form ammonium cyanide, (NH CNQ which then dissolves the suspended ferrous hydrate or ferrous sulphide, thereby forming ammonium ferrocyanide, (NH ),Fe(ON) If now the ammonia is distilled ofi, as usual, with the aid of milk of lime,(Oa(OH) calcium ferrocyanide (Ca Fe(ON) remains behind, and as the latter is sparingly soluble a portion of it is precipitated.

mained in solution the gas already relieved of ammonia and prussic acid is led into the residue (of the distillation) containing the whole of the lime-mud in order that the carbonic acid contained in the gas may precipitate the excess of caustic lime in the shape of calcium carbonate, (OaCO If now a solution of ferric chloride (Fe O1 be added, that portion of the calcium ferrocyanide which has remained in solution separates in the shape of Prussian blue, (2Fe 3Fe(CN),,) which rapidly forms a precipitate, together with the entire lime-mud. The whole of the precipitate is then treated with a solution of potassium carbonate (K 00 while boiling and stirring, whereby calcium carbonate (Ca For recovering the portion which has recipitating calcium ferrocyanide, precipitating the excess of lime in the residual solution, then precipitating the calcium ferrocyanide remaining in the solution, treating the entire precipitate with a solution of potassium carbonate so as to precipitate calcium carbonate and ferric hydrate from said solution, and crystallizing the yellow prussiate of potash from the remaining solution, substantially as set forth.

In testimony that I claim the foregoing as my invention I have signed my name in presence of two subscribing witnesses.

WILHELM soH oDER.

Witnesses:

CHAS. E. BARNES, ;WILLIAM H; MADDEN. 

